Generally, a tank container loads dangerous chemical cargoes which are combustible, explosive, poisonous, hazardous and strong corrosive. Therefore it is visualized to be “a moving time bomb”. The part in the tank container which is easiest to leak is a sealing surface of a valve assembly and a pipe connection thereof. Conventional tank containers have no means for detecting the leakage of the loaded cargoes, especially no monitoring device for detecting the sealing surface which is easiest to leak, resulting in a potential problem of being unsafe. Moreover, at present, sealing pads of PTFE or other materials are used between a flange of the tank barrel and the sealing surface of the valve assembly or other parts; bolts or other fixing means are used to connect the component parts; and a hydrostatic pressure test and gas-proof test will be conducted to the tank barrel for testing the sealing security of the sealing surface. In addition, a common practice for protecting the valve assembly is to install a valve assembly protection box with a lid such that it can turn around a hinge, use a pin assembly to lock the boxes and lids, and then attach a TIR sealer for protecting from artificial damage. However, this structure has some inherent disadvantages that it can be easily destroyed but can be recovered in a simple way, which will incur a possible danger.